This invention relates generally to protecting and clearing the lens of a camera lens when operated in a hostile environment. More particularly, the present invention is a method an apparatus for protecting and clearing a camera lens of a camera used in an environment that regularly exposes the camera lens to dirt, debris, water or other liquid or solid matter, or abrasive contact such as to impair or occlude the image of the camera.
The evolution of the camera is an odd mix of science, luck, and insight. Until George Eastman produced a camera pre-loaded with a paper-based film, cameras were largely in accessible to the general public. Shortly thereafter, he substituted celluloid for the paper base. Other improvements followed, including increased light sensitivity of the film, better printing papers and more predictable processing chemistry. The camera became a tool, not just a gadget.
The first cameras recorded still images on self-contained media. Movie cameras followed.
The camera took an evolutionary turn with the development of television. The video cameras did not record images but transmitted them. The recording of the image produced by the video camera was separated from the capture and transmission of that image.
Besides being a tool for photographic arts, cameras are a major component of security, surveillance and monitoring systems. Optical surveillance devicesxe2x80x94be they still cameras, movie cameras, or video camerasxe2x80x94are very much apart of modem life. We are watched on the highway, at the bank, in the lobby of hotels, at airports, and retail establishments. Optical surveillance allows commercial enterprises to protect their property, traffic control officials to monitor highways, and security personnel to keep a watchful eye on airports and other locations that may be targets of terrorism. Recent events have increased the demand for optical surveillance and optical surveillance devices.
Conducting optical surveillance is a difficult proposition under any conditions, but is an especially difficult task when the optical surveillance device must operate and survive a variety of environmental elements and physical hazards. Optical surveillance devices that are located out of doors are exposed to rain, snow, mud, dust, fuel, and exhaust gases just to name a few of the environmental hazards they may face. The challenge under such conditions is to protect the optical surveillance device from environmental elements, remove any liquid and/or from the optical elements of the optical surveillance device, and maintain the performance of the optical surveillance device with as little manual intervention as feasible. At present, the state of the art is to incorporate an optical surveillance device into a xe2x80x9cfair weatherxe2x80x9d system that operates only in benign weather conditions or to build a shelter over the optical surveillance device that will protect its critical components from the elements. Both of these approaches have only moderate success as even under the best of conditions.
Where the surveillance target is the undercarriage of a vehicle, the problem is compounded as vehicle traffic imparts dirt and debris to the optical surveillance device. Even shelters provide only moderate protection of the optical surveillance device as wet or snowy vehicles drip onto the lens or lens cover of the optical surveillance device rendering the optical surveillance device unusable until its lens or its cover are manually cleared. Further, the lens or lens cover is necessarily under the vehicle and thus is subject to abrasive contact from both dropped debris and vehicle tires. This wear will eventually damage the lens or lens cover. Simply recessing the lens or lens cover to protect against wear abrasion is not a viable solution as it creates a cavity thereby exacerbating the debris collection over the optical surveillance device.
What is needed is a system to clear the lens or lens cover of an optical surveillance device when covered with liquid or solid debris with a minimum of human intervention. This system must be easy to use and not interfere with the operation of the optical surveillance device or with its mission. The system must further require only minimal maintenance. The lens of the optical surveillance device must be protected from abrasive contact.
It is therefore an object of the present invention to clear the lens or lens cover of an optical surveillance device of liquid or solid debris with a minimum of human intervention.
It is a further object of the present invention to protect the lens of an optical surveillance device from abrasive contact.
It is yet another object of the present invention to protect an optical surveillance device from environmental hazards.
It is still another object of the present invention to maintain the image quality of an optical surveillance device at all times.
These and other objects of the present invention will become apparent from a review of the general and detailed description that follows. An embodiment of the present invention is a system for protecting the lens of an optical surveillance device with a lens cover of scratch-resistant transparent material, mounting the optical surveillance device in a protective mounting structure such that the lens cover of the optical surveillance device is recessed from the top opening of the protective mounting structure while maintaining the necessary field of view, and for automatically or semi-automatically clearing the lens cover of the optical surveillance device of liquid and solid debris. In the present invention, the clearing of the lens cover is achieved using a source of compressed gas and directing a high-pressure burst of gas over the lens cover. The gas flow is modulated by an air pressure regulator. When debris is detected (either visually or by the optical surveillance device), the an air pressure regulator releases a burst of gas from the gas source. The gas is passed through a vortex generator that not only directs the gas onto the lens cover of the optical surveillance device but also mixes the gas with ambient air, thereby increasing the volume of gas that passes over the lens cover. The burst of gas clears the lens cover of liquid debris by forcing the liquid from the recess created by the protective recessing spacer between the top of the protective mounting structure and the lens cover into at least one drain hole in the protective mounting structure in which the optical surveillance device is mounted. Light, solid debris may either be expelled from the recess between the top of the protective mounting structure and the lens cover. In another embodiment of the present invention, solid debris is pushed into collection chambers in the protective mounting structure for later removal. In the present invention, the presence of continued image deterioration informs the operator that automatic cleaning cannot clear the lens and that manual cleaning may be necessary. Alternatively, automatic/semi-automatic image review may perform this function and inform the operator of the need for manual cleaning by alarm or other signal.